Denervation and atrophy of paraspinal muscles after open lumbar interbody fusion is associated with clinical outcome—electromyographic and CT-volumetric investigation of 30 patients

Background Different studies have shown that atrophy of paraspinal muscles arises after open dorsal lumbar fusion, and the reasons for this atrophy are still not yet fully clarified. This prospective study investigates the extent of atrophy of the lumbar paraspinal muscles after open lumbar interbody fusion, its possible causes, and their association with clinical outcome measures. Methods Thirty consecutive patients were prospectively included (13 male, 17 female, median age 60.5 years, range 33–80 years). Mono or bisegmental, posterior lumbar interbody fusion and instrumentation was performed applying a conventional, open lumbar midline approach. Clinical outcome was assessed by the Short Form (36) Health Survey (SF-36) questionnaire and visual analogue scale. Needle electromyography of paraspinal muscles was performed preoperatively, at 6 and 12 months. Serum values of creatine kinase, lactate dehydrogenase and myoglobin were determined preoperatively, at day 2 after surgery and at discharge. Paraspinal muscle volume was determined by volumetric analysis of thin-slice computed tomography scans preoperatively and 1 year after surgery. Results There was a significant increase of electromyographic denervation activity ( p =0.024) and reduced recruitment of motor units ( p = 0.001) after 1 year. Laboratory studies showed a significant increase of CK ( p